How water bottles create cheap lighting...

The BBC's Kate McGeown reports from Manila.

   Alfredo Moser´s invention is lighting up the world. In 2002, the Brazilian mechanic had a light-bulb moment and came up with a way of illuminating his house during the day without electricity -using nothing more than plastic bottles filled with water and a tiny bit of bleach.

   So how does it work? Simple refraction of sunlight, explains Moser, as he fills an empty two-litre plastic bottle.

   "Add two capfuls of bleach to protect the water so it doesn´t turn green (with algae), The cleaner the bottle, the better", he adds.

   Wrapping his face in a cloth he makes a hole in a roof tile with a drill. Then, from the bottom upwards, he pushes the bottle into the newly-made hole.

  "You fix the bottle in with polyester resin. Even when it rains, the roof never leaks -not one drop."

   This simple initiative in the Philippines is bringing a bit of brightness into the lives of the country´s poorest people.

   In short, the project is called "Litre of Light" and the technology is just a plastic bottle filled with water.

   It´s an environmentally-friendly alternative to an electric light bulb and it´s virtually free.